pages: move home page code, introduce viewmodels

I think it's cleaner if the view concentrates on being a view, and all
the finicky logic is inside a viewmodel. This introduces that pattern
by using it in the HomePage

lib/pages/home_page.dart

@@ -0,0 +1,227 @@
+import 'dart:async';
+
+import 'package:auto_route/auto_route.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+import 'package:get_it/get_it.dart';
+import 'package:logger/logger.dart';
+import 'package:sail_ui/sail_ui.dart';
+import 'package:sidesail/console.dart';
+import 'package:sidesail/deposit_address.dart';
+import 'package:sidesail/rpc/rpc.dart';
+import 'package:sidesail/withdrawals.dart';
+import 'package:stacked/stacked.dart';
+
+@RoutePage()
+class HomePage extends StatelessWidget {
+  const HomePage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return SailPage(
+      title: 'SideSail',
+      body: ViewModelBuilder.reactive(
+        viewModelBuilder: () => HomePageViewModel(),
+        builder: ((context, viewModel, child) {
+          return Center(
+            child: SizedBox(
+              width: 1200,
+              child: Column(
+                children: [
+                  const Row(
+                    children: [
+                      Expanded(child: RpcWidget()),
+                    ],
+                  ),
+                  const Row(
+                    children: [Text('Withdrawal stuff')],
+                  ),
+                  Row(
+                    children: [
+                      Text('Withdrawal bundle status: ${viewModel.withdrawalBundleStatus}'),
+                    ],
+                  ),
+                  Row(
+                    children: [
+                      // TODO: this needs to be a P2PKH address. Validate this,
+                      // somehow.
+                      // can probably use https://github.com/dart-bitcoin/bitcoin_flutter
+                      // addressToOutputScript
+                      const Text('Mainchain address: '),
+                      Expanded(
+                        child: TextField(
+                          controller: viewModel.withdrawalAddress,
+                        ),
+                      ),
+                    ],
+                  ),
+                  Row(
+                    children: [
+                      const Text('Amount: '),
+                      Expanded(
+                        child: TextField(
+                          controller: viewModel.withdrawalAmount,
+                          inputFormatters: [
+                            // digits plus dot
+                            FilteringTextInputFormatter.allow(RegExp(r'[.0-9]')),
+                          ],
+                        ),
+                      ),
+                    ],
+                  ),
+                  Row(
+                    children: [
+                      ElevatedButton(
+                        onPressed: () => viewModel.onWithdraw(context),
+                        child: const Text('Submit withdrawal'),
+                      ),
+                    ],
+                  ),
+                  const Withdrawals(),
+                  const Row(
+                    children: [Text('Deposit stuff')],
+                  ),
+                  Row(
+                    children: [
+                      DepositAddress(viewModel.depositAddress),
+                      ElevatedButton(
+                        onPressed: viewModel.generateDepositAddress,
+                        child: const Text('Generate'),
+                      ),
+                    ],
+                  ),
+                ],
+              ),
+            ),
+          );
+        }),
+      ),
+    );
+  }
+}
+
+class HomePageViewModel extends BaseViewModel {
+  final log = Logger(level: Level.debug);
+  RPC get _rpc => GetIt.I.get<RPC>();
+
+  final TextEditingController withdrawalAddress = TextEditingController();
+  final TextEditingController withdrawalAmount = TextEditingController();
+
+  String depositAddress = 'none';
+
+  Timer? _withdrawalBundleTimer;
+  String withdrawalBundleStatus = 'unknown';
+
+  HomePageViewModel() {
+    _startWithdrawalBundleFetch();
+  }
+
+  void _startWithdrawalBundleFetch() {
+    _withdrawalBundleTimer = Timer.periodic(const Duration(seconds: 1), (timer) async {
+      final state = await _rpc.fetchWithdrawalBundleStatus();
+      withdrawalBundleStatus = state;
+      notifyListeners();
+    });
+  }
+
+  void onWithdraw(BuildContext context) async {
+    // 1. Get refund address. This can be any address we control on the SC.
+    final refund = await _rpc.callRAW('getnewaddress', ['Sidechain withdrawal refund']) as String;
+
+    log.d('got refund address: $refund');
+
+    // 2. Get SC fee estimate
+    final estimate = await _rpc.callRAW('estimatesmartfee', [6]) as Map<String, dynamic>;
+
+    if (estimate.containsKey('errors')) {
+      log.w("could not estimate fee: ${estimate["errors"]}");
+    }
+
+    final btcPerKb = estimate.containsKey('feerate') ? estimate['feerate'] as double : 0.0001; // 10 sats/byte
+
+    // Who knows!
+    const kbyteInWithdrawal = 5;
+
+    final sidechainFee = btcPerKb * kbyteInWithdrawal;
+
+    log.d('withdrawal: adding SC fee of $sidechainFee');
+
+    // 3. Get MC fee
+    // This happens with the `getaveragemainchainfees` RPC. This
+    // is passed straight on to the mainchain `getaveragefee`,
+    // which is added in the Drivechain implementation of Bitcoin
+    // Core.
+    // This, as opposed to `estimatesmartfee`, is used is because
+    // we need everyone to get the same results for withdrawal
+    // bundle validation.
+    //
+    // The above might not actually be correct... What's the best
+    // way of doing this?
+
+    const mainchainFee = 0.001;
+
+    final address = withdrawalAddress.text;
+    final amount = double.parse(withdrawalAmount.text);
+
+    // ignore: use_build_context_synchronously
+    await showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Confirm withdrawal'),
+        content: Text(
+          'Confirm withdrawal: $amount BTC to $address for $sidechainFee SC fee and $mainchainFee MC fee',
+        ),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.of(context).pop(),
+            child: const Text('Cancel'),
+          ),
+          TextButton(
+            onPressed: () async {
+              log.i(
+                'doing withdrawal: $amount BTC to $address for $sidechainFee SC fee and $mainchainFee MC fee',
+              );
+
+              final withdrawalTxid = await _rpc.callRAW('createwithdrawal', [
+                address,
+                refund,
+                amount,
+                sidechainFee,
+                mainchainFee,
+              ]);
+
+              log.i('txid: $withdrawalTxid');
+
+              // ignore: use_build_context_synchronously
+              await showDialog(
+                context: context,
+                builder: (context) => AlertDialog(
+                  title: const Text('Success'),
+                  content: Text(
+                    'Submitted withdrawal successfully! TXID: $withdrawalTxid',
+                  ),
+                  actions: [
+                    TextButton(onPressed: () => Navigator.of(context).pop(), child: const Text('OK')),
+                  ],
+                ),
+              );
+            },
+            child: const Text('OK'),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Future<void> generateDepositAddress() async {
+    var address = await _rpc.generateDepositAddress();
+    depositAddress = address;
+    notifyListeners();
+  }
+
+  @override
+  void dispose() {
+    _withdrawalBundleTimer?.cancel();
+    super.dispose();
+  }
+}

pubspec.yaml

@@ -47,6 +47,7 @@ dependencies:
   get_it: ^7.6.4
   flutter_secure_storage: ^9.0.0
   collection: ^1.17.2
+  stacked: ^3.4.1+1
 
 dev_dependencies:
   flutter_test: